The present invention relates, in general, to transmitter circuits and relates in one embodiment, to a transmitter circuit which is connected to at least one antenna device for emitting electromagnetic waves.
Such transmitter circuits have numerous uses, for example in the unlicensed frequency band which is referred to as the industrial/scientific/medical (ISM) band. Examples of these are industrial remote control systems, telemetry and low-power data transmission. Typical transmission frequencies cover a range of 300 MHz to 1 GHz, in which case European ISM standards have an operating frequency of 433 MHz. A typical transceiver circuit for the ISM band should be able to be operated at different carrier frequencies.
Further examples of the use of ISM transmitter circuits include security alarms, telemetry, environment monitoring systems, wireless data converters, access and movement monitoring systems, remote measuring systems, bar code readers, wireless keyboards, wireless computer mice, radio-controlled locking systems, tire pressure monitoring systems, garage door opening devices and doorbells. Many of these uses are based on unidirectional data transmissions from a transmitter to a receiver, while certain uses are based on bidirectional data transmissions using at least two transceivers.
For these and other reasons, there is a need for the present invention.